numpy shape

Yeeun·2025년 4월 24일

Python

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Let's clarify what .shape means, especially when you see something like (row, column, dim).

In general:

The .shape attribute returns a tuple that tells you the dimensions of the data structure (how it's organized in memory).


Let's break down common shapes:

1. 2D Data (e.g., a table)

import numpy as np
arr = np.array([[1, 2], [3, 4], [5, 6]])
print(arr.shape)  # Output: (3, 2)
  • 3 rows, 2 columns → shape = (3, 2)

2. 3D Data (e.g., image, or dataset with extra dimension)

arr3d = np.random.rand(10, 20, 3)
print(arr3d.shape)  # Output: (10, 20, 3)
  • 10 rows
  • 20 columns
  • Each cell has 3 channels (or values) → shape = (10, 20, 3)

This third value (often called dim or depth) can represent:

  • Color channels in an image (RGB = 3)
  • Features per sample in a dataset
  • Time steps in a sequence

Summary:

  • .shape tells you how many rows, columns, and dimensions (if any) your data has.
  • (rows, columns) for 2D
  • (rows, columns, dim) for 3D

Would you like a diagram or real-world analogy to help make this even clearer?

Great follow-up! A 1D array in NumPy (or in general) is the simplest type of array—it’s just a single list of values arranged in one line. Let's break it down gently:


✅ What a 1D array implies:

  • It only contains values—no rows or columns to speak of.
  • You can think of it like a row of boxes:
    [3, 7, 1, 9] ← four values, all in one "line."

❓ So is there a channel like in images?

  • No, not in a 1D array. There is no concept of channels, rows, or columns.
  • It’s just one axis (axis = 0).
    You index like this: arr[0], arr[1], etc.

📌 Axis in 1D:

  • Only one axis: axis 0 → the direction you move when you go from one item to the next.

Real-World Analogy 🧃

Imagine a vending machine row with juice boxes lined up:

| Juice | Juice | Juice | Juice |
   0       1       2       3    ← index

There’s just one line. That’s a 1D array.


Would you like me to compare that with 2D or 3D (like with image channels) so you can see how it evolves from here?

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